The above
diagram shows an artificial satellite in a polar orbit. It travels from north
to south around one side of the Earth then back to north round the other side.
Polar orbital satellites are often very fast moving, completing an orbit within
a couple of hours or less. Whilst this is happening, the Earth is spinning so
it seems that the satellite is seen to travel in a spiral pathway. This means
that it covers a large part of the Earth's surface each day. This sort of orbit
is useful for remote sensing satellites e.g. Landsat. The data collected is
used to study things like crops, water and air pollution, the impact of industry
on the environment and reserves of natural resources such as fossil fuels

The above
diagram shows an artificial satellite in a geostationary orbit. It is positioned
much further out and orits between the two poles. The orbit may be inclined
at an angle to the equator or parallel to it as shown above. Its distance is
such that it completes one complete orbit in 24 hours. In the same time, the
Earth completed one complete rotation so the net result is that the satellite
stays above a single point on the surface of the Earth. This is particularly
useful for weather satellites that monitor the weather of a particular area,
navigational satellites (GPS - global positioning satellites) and communications
satellites.